Objective To review the current evidence that links smoking to obstructive sleep apnea (OSA) and to discuss some potential mechanisms proposed for these links.Data sources We searched PubMed and Medline to identify studies investigating the interaction between smoking and OSA.Study selection Articles regarding the relationship between smoking and OSA were selected.Studies considered smoking as a confounding factor were excluded.Results The association of smoking and OSA has been confirmed in several studies.The effects of smoking on the pathophysiology of OSA may include smoking-induced upper airway inflammation,stimulant effects of nicotine on upper airway muscles,and a "rebound effect" due to nightly short-term nicotine withdrawal,or all of the above.In addition,the coexistence of OSA and smoking may have more widespread implications for cardiovascular dysfunction in patients with OSA.Finally,OSA might be responsible for the addiction to nicotine.Conclusions Smoking may act as a risk factor for OSA and join with OSA in a common pathway to increase the risk of systematic injury.OSA,in turn,may be a predisposing factor for smoking.Thus,smoking cessation is recommended when considering treatment for OSA,and treating OSA may be a necessary precondition for successful smoking cessation.